In-situ generation of fluorinated polycarbonate copolymer solid electrolytes for high-voltage Li-metal batteries

Polymer-based solid-state lithium metal batteries (LMBs) are considered as an ideal power source for portable and flexible devices due to the consecutively increasing energy demand. However, the relatively narrow electrochemical window of conventional polyethylene-oxide-based polymer electrolytes limits the application of high-energy-density cathode materials for LMBs. To overcome these limitations, herein, we designed a fluorine-containing polycarbonate-based electrolyte to expand the electrochemical window up to above 5 V (vs. Li/Li+); this electrolyte exhibits an ionic conductivity of 5.02 × 10−5 S cm−1 at room temperature. The addition of fluorine-containing groups significantly increased the oxidation potential of the electrolyte. The corresponding NCM811 LMBs assembled through in-situ polymerization on the surface of lithium metals exhibited a specific capacity of 218 mAh g − 1 at 0.1 C (1 C = 275 mA g − 1), with a capacity retention of >70% after 300 cycles under ambient circumstance. The proposed polycarbonate electrolyte has considerable potential for the further application in LMBs comprising high-voltage cathode materials.